Gravel pack well completion method



June 12, 1956 T. 5. WEST 2,749,988

GRAVEL PACK WELL. COMPLETION METHOD Filed April 9, 1952 2 Sheets-Sheet 1 Tho/770.: J. Wesz INVENTOR.

2 Sheets-Sheet 2 Thomas J. i/Vesf IN V ENTOR.

A 7'TOR/VE V June 12, 1956 T. 5. WEST GRAVEL PACK WELL. COMPLETION METHOD Filed April 9, 1952 United States Patent GRAVEL PACK WELL COMPLETION METHOD Thomas S. West, San Antonio, Tex.

Application April 9, 1952, Serial No. 281,293

4 Claims. (Cl. 166-20) This invention relates to well completion methods, and this application disclosing such methods is a continuationin-part application of my co-pending application Serial No. 748,217 for Gravel Pack Completion Method, filed May 15, 1947, now issued as Patent No. 2,597,554, under date of May 20, 1952.

The invention in general has the object of providing a method of preventing the vertical flow of gas and/ or water into an oil producing zone adjacent a well bore by inserting a tubing open at substantially its lower end into the well bore adjacent the producing formation, graveling the annular space outwardly of the tubing at a desired elevation, and circulating a fluid down the annular space between the tubing and the well bore wall and out into the formation immediately adjacent the graveled portion of the bore to maintain a fluid saturation in the adjacent formation area.

in detail the invention has as its object the providing of a method of minimizing or preventing the vertical flow of gas into an oil producing zone adjacent a well bore by inserting a perforated screening section into the well bore, filling the space between the well bore wall below the casing and the screening section with alternate, superimposed, and substantially horizontally disposed layers of granular material wherein the flow passages of one of the alternate layers of granular material are effectively larger than the flow passages of the next adjacent layer and larger than the effective flow passages of the adjacent producing formation, inserting a tubing having an open lower end into the screening section, sealing off between the tubing and the screening section at a point spaced below the cars ing, and circulating a fluid down the annular space between tubing and screening section and out through the perforations above the sealing means and into the adjacent formation to maintain a fluid saturation in the adjacent formation area.

Furthermore, in detail, the invention has the object of providing a method of minimizing or preventing the vertical flow of gas into an oil producing zone adjacent a well bore by inserting a tubing having an open lower end into the perforated portion of a Well bore casing (and where the surrounding cement has also been perforated, if the casing has been cemented into the well bore), sealing off the annular space between the tubing and casing at a point spaced below the top of the perforated portion, and circulating a fluid down the annular space between tubing and casing and out through the perforations above the sealing means into the adjacent formation to maintain a fluid saturation in the adjacent formation area.

In additional detail, the invention has the object of providing a method of minimizing or preventing the vertical flow of water into an oil producing zone adjacent a well bore by inserting a tubing having an open lower end into the perforated portion of the well bore casing (and where the surrounding cement has also been perforated, if the casing has been cemented into the well bore), sealing off the annular space between the tubing and easing at a point spaced below the top of perforated portion, and

2,749,988 Patented June 12, 1956 circulating a fluid down the tubing and into the well bore below the sealing means and out into the adjacent formation to maintain a fluid saturation in the adjacent formation area.

Also, in detail, the invention has as its object the providing of a method of minimizing or preventing the vertical flow of water into an oil producing Zone adjacent a well bore by inserting a perforated screening section into the well bore, filling the space between the well bore below the casing and the screening section with alternate, superimposed, and substantially horizontally disposed layers of granular material wherein the flow passages of one of the alternate layers of granular material are effectively larger than the flow passages of the next adjacent layer and larger than the effective flow passages of the adjacent producing formation, inserting into the section a tubing having a perforated portion, sealing ofi between the tubing and screening section both above and below the perforated portion, and circulating a fluid down the annular space between the tubing and the screening section above the upper sealing means, and into a by-pass in the tubing, and downwardly therethrough and out through the tubing end below the by-pass and through the layers and into the adjacent formation to maintain a fluid saturation in the adjacent formation.

Additionally, in detail, the invention has the object of providing a method of minimizing or preventing of the vertical flow of gas into an oil producing zone adjacent a well bore by inserting a tubing open at its lower end into the well bore, sealing off between the tubing and the well bore, and circulating a fluid down the annular space between the tubing and the well bore and out of the well bore above the sealing means into the adjacent formation to maintain a fluid saturation in the adjacent formation area.

In further additional detail, the invention has the object of providing a method of minimizing or preventing the vertical flow of water into an oil producing zone adjacent a well bore by inserting a tubing open at its lower end into the well bore, sealing off between the tubing and the well bore, and circulating a fluid down the tubing and into the well bore below the sealing means and into the adjacent formation to maintain a fluid saturation in the adjacent formation area.

Other and further objects will be apparent when the specification is considered in connection with the drawings in which:

Fig. l is a partially diagrammatic sectional elevation showing a preferred form and usage of the invention.

Fig. 2 is a fragmentary, partially diagrammatic sectional elevation showing another form and usage of the invention.

Fig. 3 is a fragmentary, partially diagrammatic, sectional elevation showing another modification and usage of the form of invention shown in Fig. 1.

Fig. 4 is a fragmentary, partially diagrammatic, sectional elevation showing another modification and usage of the form of the invention shown in Fig. 1.

Fig. 5 is a fragmentary, partially diagrammatic, sectional elevation showing another modification and usage of the form of the invention shown in Fig. 2.

Fig. 6 is a fragmentary, partially diagrammatic, sectional elevation showing another modification and usage of the form of the invention shown in Fig. 2.

As gas is lighter than oil, it generally will be found at the top of a formation sand above the oil, and under static conditions the oil-gas contact surface may be considered as extending in a substantially horizontal plane. However if there is substantial oil flow into the well bore below the level of the gas-oil contact surface, such surface will curve sharply downwardly in the immediate vicinity of the well bore. This occurs primarily because the flow of oil into the well bore reduces the pressure at such point, and it also occurs because the gas has a lower viscosity than oil, and the sand olfers lessresistance to its flow.

Consequently, under certain conditions, the gas-oil contact surface surrounding the well bore will take the shape of an inverted cone and free gas will be produced. In the petroleum production industry this undesirable condition is known as vertically downward coming.

Water, on the other hand, is heavier than oil and may be found immediately below the oil in a sand formation, and under static conditions the water-oil contact surface may be considered as extending in a substantially horizontal plane. However, if there is substantial oil flow into the well bore above the level of the Water-oil contact surface, such surface will curve sharply upwardly in the immediate vicinity of the well bore. This tends to occur primarily because the flow of oil into the well bore reduces the pressure at such point, and such tendency is increased because the water has a lower viscosity than the oil, and the sand offers less resistance to its flow.

Consequently, under certain conditions, the water-oil contact surface surrounding the well bore will take the shape of a cone and water will be produced. In the petroleum production industry this undesirable condition is known as vertically upward coning.

Fig. 1 shows one form of apparatus and method adapted to prevent vertically downward coming of gas. The well bore 2 has been drilled through a formation 3 having a lower, oil containing portion 4 and an upper gas containing portion 5. The line 6 denotes the demarcation surface between the gas sand and the oil sand 4. The casing 10 has been set and cemented in the top of the producing formation 3, the cement being shown at 11. For the purposes of this invention the exact point at which the casing has been set is not critical, and it is herein pointed out that the procedure to be hereinbelow described may also be employed in uncased wells. It is usually preferable, however, to set and cement casing proximate the producing formation.

Layers are then provided which may comprise alternate layers of porous cement or plastic having different effective pore space sizes or filtration characteristics. The preferred embodiment is however that in which the alternate layers are composed of granular material, the permeability or filtration characteristics of the layers being regulated by varying the particle size, or particle size range, of the granular material. Because of their relatively low cost and resistance to corrosion and chemical action, siliceous materials such as gravel, sand, silt, including particles in the colloidal range, have been found to be a preferable granular material. The use of layers of granular material has the advantage over rigid cementing material in that such layers are fluid in nature and therefore avoid the formation of open channels or cracks. Granular material also has the important advantage of permitting the selection of a particle size range which will effectively screen unconsolidated sand.

In case of unconsolidated sands in the producing formation 3, the particle size of the gravel must be such as to prevent the infiltration of sand from the formation and into the gravel layers. The proper gravel size for screening a given sand may be determined experimentally. The selection of gravel on the basis of a screen analysis of the sand is also well known to the art, having been discussed in numerous publications such as AIME Technical publication No. 2904 by Thomas S. West. After selection of gravel, the liner 16 is allotted with slots of such width as to prevent the entry of gravel of the selected'particle size. Gravel of this size is used for the alternate layers such as 31 which have the greater permeability.

Whereas the slots 18 are shown in the liner 16, this invention is not limited to such construction but consid- 4 ered any type of well screen structure in addition to the slotted, bored, or perforated liner section shown.

For providing layers of the lesser permeability or effective pore size such as 27, a mixture of sand and gravel is usually employed. The quantity of sand mixed with the gravel is preferably just suflicient to fill the pore spaces of the gravel. With this quantity of sand the possibility of settling of the mixed sand and gravel layers due to the flowing out of the sand is minimized. The purpose of this mixture is to provide a layer on which an injection fluid laden with fine particle material will form a filter cake of lower permeability while the layer will not flow through the slots of liner 16.

The gravel content of the mixed layers such as 27 forms a bridge around the slots of the liner preventing the entry of sand content of the mixture. The sand content of this layer results in the formation of a filter cake by any fluid containing solid particles of the proper size range. Mixed layers such as 27 may be adjusted to a permeability approximating that of the producing sand with the result that the rate of fluid production from the formation opposite this layer is reduced only slightly. If desired, however, the permeability of mixed layers may be reduced to any desired extent by use of a properly graded particle size material. For example, mixtures of gravel, sand, silt, bentonite and cup grease have been prepared which approximate zero permeability.

To prevent the separation of the particles comprising mixed layers such as 27 during the process of deposition because of the coarser particles settling at a greater rate than the fine ones, it is necessary to mix some kind of binding material with the gravel, sand, or other material. This binding material is preferably one which can be removed if desired after deposition. Bentonite, starches, gums, sugars and other gummy substances and greases have been satisfactorily used for this purpose. Pellets coated with a soluble material have also proved satisfactory. However, the preferable binder thus far employed has been found to be a lime soap base cup grease. This grease not only effectively prevents separation of sand and gravel when deposited in water, aqueous solutions, or water base mud but will also flow out of the mixture under relatively low pressure gradient leaving a permeable layer. When used in low pressure wells it is preferable to use additional means for removal of grease or other binder. The various methods of removing paraflin from oil wells have been found satisfactory for this purpose. A preferred method of removal of grease is the dumping of the clean gravel layer such as 31 with the pore space of this gravel filled with carbon tetrachloride, or trichloroethylene. Since such a grease solvent has a greater density than water or usual drilling mud, it settles to bottom and is therefore more effective than light solvent which would rise.

After the casing 10 is in position, the perforated liner, screen, or screening section 16 is lowered to the desired level opposite the producing formation 3. Then the alternate gravel layers 27 and 31 may be deposited by conventional means, as described in my Patents Numbers 2,597,554 and 2,623,595.

After placing the various layers of granular material, the seal 17 is provided to seal the well space surrounding liner 16 and above the uppermost layer. This seal may be any form of packer or other sealing agent but is preferably a mixture of a quick set cement and sand, the function of the sand being to bridge the pore spaces of the gravel to prevent the entry of cement. Then the tubing 40 having the packer assembly 41 thereon, is lowered, by means at the top of the well to be hereinbelow described, into the screening section 16 to the position shown in Fig. 1 for sealing the space between tubing 40 and liner 16. The length of the packer 41 is preferably greater than the height of the thickest of the clean gravel layers 31, otherwise a seal will not result if the packer 41 is positioned opposite of the layers 31. A series of cup '5 or lip type packers have been found satisfactory for packer assembly 41.

As shown in Fig. 1, the well head 56 at the top of the well may have supported above the head 56' the tubing block 65 which has the opening 66 therein through which passes the tubing 40, the packing 67 being provided within the opening 66 to be held down and around the tubing by the gland 65. The slips 69, within the gland 68 grasp the tubing 49, but permit it to move vertically therethrough.

The tubing 40 is lowered and raised by the jack 55 which comprises the handle 70 pivotal on the piston 71 and connected by the link 72 to the block 65. The vertical movement of the piston 71 in the cylinder 73 transfers fluid from the reservoir 74, through the valves 75 and 76 to the lower portions of the cylinders 77 and 78 which extend upwardly from the block 65. The pistons 79 and 80 within the cylinders 77 and 78 respectively, support the frame 81 thereabove which has the opening 82 therein to receive the tubing 40 therethrough and to receive and support the slips 83 which grasp the tubing to lift it as the frame is moved upwardly by the operation of the jack 55. To lower the tubing the valve 84 is opened to permit the fluid to pass back from beneath the pistons 79 and 80, through the lines 85 and 86, to the reservoir 74.

The pump 87 takes suction at 88 from the viscous fluid reservoir 89 and discharges it at 90 to the filter 91 below the starting valve 92. The opening of the valve 93 in the line 93' permits the viscous fluid to enter the head 56' and the well bore. The by-pass line 94, when the valve 95 is opened, permits direct discharge of the viscous fluid therethrough to the line 93.

The return of the viscous fluid follows the path of the tubing past the open valve 96 and through the swivel 97 and hose 98 to a convenient basin, or directly to the reservoir 89.

If excessive gas is found to be produced with the oil, or other undesired production occurs, because of vertically downward coning in the producing formation surrounding the well, it becomes desirable to use a sealing or flow retarding substance which actually flows into the pore spaces of the sand. Because of the difficulty of controlling fluid flow outside of the well bore it is also desirable that permanent plugging of the formation does not result.

The control of vertical coning by inducing a flow of viscous fluid through sand 3 may be secured by providing oil, oil-water emulsion, or other viscous fluid 60, the general direction of flow of such viscous fluid being the path generally shown at 61.

Because a fluid having a viscosity many hundreds of times greater than that of gas or water may be used, the volume of viscous fluid which would be circulated through the sand above the packer 41 to the space below this packer is very much less than the volume of gas or water which would enter by coning or which would normally be produced from these zones. Obviously, of course, the viscous fluid saturation may be provided to prevent coning of undesired fluids in a gas well.

The fluid may pick up from the well bore, or may have admixed therewith, materials of a particle size which will flow through the liner perforations and through the layers 27 and 31, but which, in time, will build up a filter cake on both the substantially horizontal surfaces separating the layers 27 and 31, and on the substantially vertical surfaces separating the layers 31 from the formation 3. Then the flow direction, as affects these vertical surfaces, may be reversed.

This may be accomplished by raising the tubing 40 above the layers, so that formation pressure forces fluid to flow through such surfaces toward the tubing to wash away the filter cake from the vertical surfaces, or else it may be accomplished by supplying a force at the top of the well which will draw formation fluids through such vertical surfaces and through the liner perforations into the annular space between the tubing and liner, thereby also washing away the filter cake from these vertical surfaces.

Vertical flow does not therefore result through layers 27. Oil or other viscous fluid is supplied to the sand of the formation 3 through the layers 31, above the point of shut off of the packer 41. A viscous fluid saturation may thus be maintained in the portion of the sand section in which vertical coning would normally occur, namely, the gas sand 5.

Then, with the tubing positioned as shown in Fig. 1, and with the downward and outward supply of the vis cous fluid resumed, the fluid will flow outwardly through the vertical surfaces of the sand 3 while the filter cake on the horizontal surfaces of layers 27 above the level of packer 41 is not appreciably affected by the back flowing hereinabove described, and will therefore resist the vertical flow of the viscous fluid and thereby divert it more effectively out into the adjacent formation to maintain a fluid saturated adjacent area thereby minimizing or preventing the flow of gas into the well bore below the sealing means. The dotted line Shows the shape of the inverted cone space through which gas would tend to flow if the method hereinabove described were not employed.

The apparatus and method shown in Fig. 1 may employ a filter pack of uniform constituency rather than the alternate layers 27 and 31 hereinabove described. In such case the filter pack should be of a granular material of substantially the same permeability as the producing formation and the packer should be of substantially greater vertical height than the radial dimension of the filter pack. Thus the radial distance of flow through the filter pack being substantially shorter than the vertical distance, a greater portion of the circulated fluid will enter the formation to be saturated than penetrates downwardly to enter the well bore below the packer.

In cases in which it is desired to exclude water production from the lower portion 7 of sand 3, the apparatus shown in Fig. 2 is employed. This apparatus shuts oif the water which may be produced from the lower portion 7 of a formation sand 3 or it may simultaneously shut off both water and gas. The tubing 40 carries two spaced apart packers 44 and 45, so constructed as to isolate and secure fluid production from the space between them while at the same time maintaining a seal against flow from the producing formation above and below this space. By-pass 51 is provided for permitting the flow of fluid from the space above the upper packer 44 to the space below lower packer 45.

By employing a viscous fluid, and back flowing to remove the filter cake 32 from the face of the producing formation, a circulation of viscous fluid may be induced to prevent vertical coning of water and/or gas 80 in a manner similar to that shown by Fig. l for the prevention of gas coning.

As shown in Fig. 3, the method of saturation to prevent the vertically downward coning of gas can be employed in an open hole or well bore 2 which penetrates a formation 3 comprising an upper gas sand 5 and a lower oil sand 4. In this case the fluid 50 is circulated down the annular space between tubing 40 and casing 10 and out above the packer 41 into the adjacent formation to maintain a saturated formation area to prevent coning which would otherwise tend to be defined by the surface 80.

As shown in Fig. 4, a casing 10 which has been plugged at the bottom by the cement plug 83 and also cemented at 11 into the bore 2, may be perforated by the perforations 81, 82 at a predetermined point and through a desired vertical distance. Then the tubing 40 having the packer 41 thereon may be inserted in the casing 10 and positioned as shown in Fig. 4. In this case the fluid 50 is circulated down the annular space between tubing 40 and casing 10 and out through the perforations 81 above the packer 41 into the adjacent formation to maintain a saturated formation area to prevent coning which would otherwise tend to be defined by the surface 80. In this case the oil produced enters the well bore 2 below the packer 41 through the perforations 82.

As shown in Fig. .5, a casing '10, as shown in Fig. 4, is perforated adjacent an oil-water formation 3. To mini- -mize or prevent the vertically upward coning of water, as otherwise might be indicated by the surface 85, the tubing 40 having the packer 41 thereon is positioned as shown generally above the water sand 7 and a fluid 50 is supplied down the tubing 40 to circulate outwardly through the perforations 82 into the adjacent formation area as indicated. In this case the oil produced enters the annular space between tubing and easing through the perforations 8-1.

As shown in Fig. 6, a-well bore 2 may or may not have penetrated a water sand 7 below an oil sand. The tubing 40 having the packer 41 thereon is positioned as shown in the oil sand 4 above the oil-water division surface 6 and above the water sand 7. The fluid 50 is circulated down the tubing 40 and out into the adjacent formation to maintain a saturated formation area to prevent the vertically upward coning of water as might otherwise occur as indicated by the surface 85. Obviously, the same oc currence can be prevented in the same way if the well bore 2 had penetrated the water sand 7.

As it is not desirable for purposes of control to circulate the oil produced up the casing annulus, but is rather preferable to pump or flow the oil up through the tubing 40, a crossing means, not shown in Figs. and 6, but now conventional as indicated in Patent No. 2,543,382 to Schabarum, may be provided above the packer 41, whereby the oil can be returned into the tubing on its upward passage while this structure also permits the fluid to be supplied into the casing annulus from the top of the well and diverted into the tubing above the oil.

Since vertical coning of water or gas into the oil zone which is exposed for production occurs entirely within the producing formation procedures for sealing between the casing or lines and the well wall, such as cementing, are not effective for prevention of coning. Well completion procedures by which cement, or plastics, are forced into the pore spaces or natural or artificial fractures in the producing formation have also not generally proved effective in practice for preventing coning.

Coning could be theoretically minimized by the use of cement, plastics, or similar materials, if these materials are forced into the producing formation between the gas zone and the section of the oil sand exposed for production to form a non-permeable sheet or layer surrounding the well at the desired level. In practice this result is virtually never obtained.

The partial blocking of the sand face as a result of drilling mud, filter cake, or filter cake formed from other fine particle material such as pipe scale, silt, and the like, prevents even liquid cementing materials of low viscosity from completely invading the producing formation pores in the desired zone. Paths for downward coning of gas or upward coning of water therefore remain. Even if sufficiently complete penetration of a cementing material such as plastics were attained it would not be possible to effectively control the distribution of this material in the producing formation. Invasion into the oil producing zone could therefore occur resulting in shutting off the oil production.

It'has been attempted to form a horizontal sheet to separate an oil zone from a gas zone by pumping cement, or 'the'like, under pressure, down the tubing or casing, with the object that the cement will fracture the formation horizontally, and flow into the plane of fracture to form a substantially impermeable horizontal barrier betweensuch zone.

Because ofjthe difficulties with present procedures such as outlined above, no effective means for controlling or minimizing vertical coning has previously been devised which is applicable to usual field conditions. This :invention accomplishes the control of vertical coning by maintaining-a-fluid flow into-the formation through the zone in which coning occurs. By continually injecting fluid and thus maintaining saturation with the fluid in the zone in which coning would normally occur, vertical coning is positively prevented.

Since a fluid which does not solidify under well conditions may be employed, entry of the injected fluid into the oil producing zone has no tendency to plug the producing formation. By injecting a fluid which may be recovered from the oil and other well fluids any of the injection fluid which enters the well bore with the oil production may be recovered and reinjected. By using a portion of the crude oil produced as an injection fluid separation from produced oil is not necessary.

Various injection fluids such as oil-water emulsions, highly viscous plastic fluids which have low solubility in both oil and water such as Monsanto Chemical Company santicizer liquids, silicone oils, and the like, have been found useful under certain conditions. Natural gas, or mixtures of oil and gas, are also desirable injection fluids in some cases.

For example, with the completion of Figs. 5 and 6, gas may be injected down the tubing into the water section of the sand. When gas under a suflicient pressure is injected in this way the dual role of suppressing the water cone and lifting the oil to thesurface is performed.

Some of the injected gas flows upwardly into the oil sand and into the well bore with the oil production. The resulting mixture of oil and gas reduces the density of the oil column in the casing and tubing annulus. When the hydrostatic head of this fluid column becomes less than the bottom hole pressure, the flow of oil and gas from the casing at the surface results. By employing jet collars or flow valves at the proper levels in the tubing string the gas pressure required may be reduced and more efficient utilization of gas secured.

Flow valves and jet collars suitable for efficiently injecting gas from a tubing string into the surrounding fluid column are well known to the art of oil production. Mixtures of gas and oil may also be employed for decreasing the well head pressure required for injection and also decreasing the volume of fluid injection required.

The latter results because the viscosity of oil is higher than that of gas and because of the so-called Jamin effect. The Iamin effect refers to the increased resistance to flow through capillary passages of a liquid containing gas bubbles.

Generally high viscosity is a desirable quality of the injection fluid unless this fluid is also used for other purposes such as lifting the oil. The higher the viscosity the less the required volume of injection or circulation fluid for a given difference in pressure between the fluid in the producing formation and the injection fluid. The injection fluid should also be non-corrosive and should not have undesirable chemical reactions with, or other action on, the producing formation.

The preferred form of the invention shown by Fig. 1 is universally applicable to all usual types of oil producing formations including unconsolidated sands. By selecting a gravel size which will effectively screen the producing sand, for example, no possibility exists for the formation of a channel through which injection fluid may pass directly from the casing-tubing annulus into the tubing without flowing into the producing formation.

This completion also has the advantage that the packer for sealing between the tubing and the gravel screen seats in a uniform metallic tubular section rather than against the'producing formation. Seating and sealing action may therefore be positively obtained at any desired level.

The modifications shown by Figs. 3, 4, 5, and 6 are particularly applicable in practice to limestone reservoirs or relatively hard sands. If the producing formation of wells ranges from firm to unconsolidated sand, erosion by fluid flow into the bore hole ultimately develops a channel permitting flow past the packer, or in case of Figs. 4 and 5, forms a similar channel between the cement sheath surrounding the casing and the sand face.

Whereas, throughout, the formation through which the oil, water, or gas flows, has been referred to generally as a sand, this invention is not limited to sand but includes any other type of formation through which a fluid to be produced may flow.

This invention is not limited to the handling of the fluids enumerated, as gas, oil, and Water, by any special type of injection fluid, but broadly this invention includes a method of injecting a fluid of a certain viscosity range into the producing area adjacent a Well bore to minimize or prevent coning of undesired fluids to mix with the fluid it is desired to produce.

What is claimed is:

1. The method of controlling coming of Well fluids in which two separate fluid passages between the surface and the producing formation are provided, which comprises placing a filter pack to fill the well space adjacent the producing formation, injecting pressure fluid through one of said fluid passages for horizontal flow through the filter pack into the producing formation at one vertical interval and producing well fluids through the other fluid passage through the filter pack from a dilferent vertical interval of the producing formation.

2. A method of producing well fluids according to claim 1 in which the step of placing the filter pack is efliected by filling the space with granular material of such particle size distribution as to produce at least one region of relatively high resistance to fluid flow in the vertical direction between flow paths to and from the producing formation.

3. A method of producing well fluids according to claim 1 in which the step of placing the filter pack is by depositing separate horizontal layers of granular material 1,0 of particle sizes differing in adjacent layers to produce alternate layers having relatively low resistance and the others of relatively high resistance to fluid flow and thereby form a filter pack having a relatively high resistance to vertical fluid flow and a relatively low resistance to horizontal fluid flow.

4. The well completion method to control coning of pressure fluids from a well hole formation level adjacent the production level of the well, comprising packing the Well hole space between the wall of the hole and the wall of the Well tubing at the adjacent formation levels with permeable material arranged in superposed layers of different permeability to restrict vertical fluid flow in said space from a layer of greater permeability and through a layer of lesser permeability and concomitantly to provide vertically continuous support of the formation wall against channeling and cave-in thereof, sealing the tube near its well communicating end with the intermediate layers of permeable material, injecting fluid under pressure from the surface through one of the two passages afforded respectively by the tubing and the well bore for outward passage through said permeable material and into the formation at one of said levels to overcome coning pressure therein and displace coning fluid and producing flow of well fluid from the formation at the other level through said permeable material and the other of said passages.

References Cited in the file of this patent UNITED STATES PATENTS 1,816,260 Lee July 28, 1931 2,171,416 Lee Aug. 29, 1939 2,213,987 Layne Sept. 10, 1940 2,512,801 Kinney et a1. June 27, 1950 2,543,382 Schabarum Feb. 27, 1951 2,597,554 West May 20, 1952 2,623,595 West Dec. 30, 1952 

1. THE METHOD OF CONTROLLING CONING OF WELL FLUIDS IN WHICH TWO SEPARATE FLUID PASSAGES BETWEEN THE SURFACE AND THE PRODUCING FORMATION ARE PROVIDED, WHICH COMPRISES PLACING A FILTER PACK TO FILL THE WELL SPACE ADJACENT THE PRODUCING FORMATION, INJECTING PRESSURE FLUID THROUGH ONE OF SAID FLUID PASSAGES FOR HORIZONTAL FLOW THROUGH THE FILTER PACK INTO THE PRODUCING FORMATION AT ONE VERTICAL INTERVAL AND PRODUCING WELL FLUIDS THROUGH THE OTHER FLUID PASSAGE THROUGH THE FILTER PACK FROM A DIFFERENT VERTICAL INTERVAL OF THE PRODUCING FORMATION. 